In coin-operated vending machines, gambling devices and the like, inserted coins are checked for genuineness in a coin acceptor. Non-genuine coins are rejected whereas genuine coins initiate a purchasing procedure or some other function. The genuineness of coins can be checked with a mechanical coin acceptor or with an electronic coin acceptor. Prior art mechanical acceptors have used coin balances for checking the weight and the diameter of coins, slots for checking the thickness of coins and permanent magnets for determining the material. Prior art electronic acceptors have used electromagnetic or optical probes which determine the condition of the material, the diameter and the thickness of the coins and/or the condition of the coin edge. The output signals of the sensors are compared to reference values in an electronic circuit, for example, a circuit having a microprocessor. The circuit controls various flaps in accordance with the comparison in order to reject improper articles and to guide coins which fall within the tolerances of the reference values to a sorting mechanism or safe.
Electronic coin acceptors have the advantage that they can be made smaller in size because coins of different values roll along a common coin path. Of course, the reliability of an electronic test rises with the number of checking criteria. If only one checking criterion is selected such as type of material, it is often not possible to discriminate coins of foreign currencies but made of a similar material. If the diameter or the thickness or a further feature is added, a more reliable test is usually possible. Care should be taken when testing coins that the reference limits are not too narrow because the qualities of coins are subject to tolerances and vary in usage due to wear.
Swiss Application CH 6245 00 A5 shows a coin acceptor in which a section of the coin path is designed as a weighing table. However, since the coin is not held during its course over the weighing table, it is difficult to obtain an exact weight signal with this device.
European Application EP 0 038 911 shows the use of a spring above and at the end of a coin path which spring is deflected by a coin rolling down the coin path. Two sensors are associated with the spring which measure the deflection. The time which elapses during deflection in one direction and then back to the initial position is measured. This time is proportional to the mass of the coin. A flap is positioned at the end of the path which flap opens after the measurement has taken place in order to guide the coin to a valid money conduit or to a return conduit. The method is relatively complicated because the coin remains almost stationary during the measuring time. This can have an adverse effect on the insertion speed. Moreover, an additional actuation for the flap associated with the spring is necessary.